Application of adhesives in MEMS and MOEMS assembly: a review

This paper presents a review of the recent literature on the use of adhesives in MEMS packaging applications. The aim of this review has been to establish the current applications of adhesives in MEMS and MOEMS assembly and to investigate the limitations and future requirements of these materials. The review has shown that while there is a wealth of information available on the packaging of MEMS devices, there is very limited detail available within the public domain regarding the specific uses of adhesives and in particular exactly which products are in use. The paper begins with an overview of the uses of adhesives in MEMS packaging, subdivided into sections on structural adhesives, adhesives for optical applications and other applications. The paper then describes methods for adhesive dispensing and issues with adhesive use which affect the reliability of the package. The reliability of MEMS devices assembled using adhesives is a challenging issue, being more than a simple combination of electrical, mechanical and material reliability. Many failure modes in MEMS devices can be attributed to the adhesives used in the assembly; for example, thermal expansion mismatches can cause stress in the die attach, while outgassing from epoxies can cause failure of sealed devices and contamination of optical surfaces.